The present invention relates generally to arrangements for interlocking panels, and more particularly to an interlocking arrangement for panels wherein a tongued locking tab forms a cooperative slide locking engagement with two slits. The present invention also relates to a carton employing the interlocking arrangement for panels.
In the packaging of articles, and particularly of one or more articles in wrap-around type cartons, interlocking arrangements are frequently used for maintaining closure of the carton about the articles. It can be appreciated that such interlocking arrangements must be securely and reliably engaged, and must remain in such condition until the carton is opened.
One well-known form of interlocking arrangement comprises a locking tab and cooperating slit. An example of this type of locking arrangement can be seen in U.S. Pat. No. 3,249,284. In this example, as is typical, the locking tab includes a head portion attached along a relatively narrow neck to a panel of the carton. The tab includes at least one shoulder, i.e., that portion of the tab where the head connects with the relatively narrow neck. On an opposite panel of the carton, a slit is formed into which the tab may be inserted. Following insertion, the tab shoulder engages the end of the slit, preventing the tab from being withdrawn, and thereby securing the lock.
In interlocking arrangements of this type, the length of the slit is equal to or slightly greater than the width of the head portion of the locking tab to allow the tab to be inserted thereinto. As a result, the tab may be laterally movable when it is fully inserted up to its neck. Such lateral movement could result in disengagement of the tab shoulder from the slit. For this reason, it is advantageous to provide means to restrict lateral movement of the locking tab. One way in which the locking tab can be laterally restrained is to arrange a row of locking tabs such that each of the opposite end locking tabs is provided with only one shoulder so that the shoulderless side edge of that tab abuts the adjacent end of the associated slit and thereby restrains all the tabs in the row from lateral movement. An example of such an approach can be seen in U.S. Pat. No. 4,732,316. One disadvantage of this approach, however, is less locking strength of the interlocking arrangement due to the reduction in number of the locking points.
What is needed, therefore, is an improved interlocking arrangement which increases the security of the interlocking arrangement against inadvertent disengagement. Such an arrangement should be capable of restraining the locking tab from moving within the locking slit without reducing the number of the locking points.